The invention relates to a system for fixing a cap on a container head on which there is a neck surrounding a distribution orifice. This system enables an irreversible attachment in the sense that the said cap cannot be detached from the assembly without deliberately applying large forces that could at least partially damage the head and/or the overcap. But this attachment is not a complete immobilization; when fixed, the overcap can be moved in a circular or helical movement with a limited amplitude with respect to the centreline of the neck in the head.
The use of this type of head is known for xe2x80x9cquarter turnxe2x80x9d or xe2x80x9ccenterlockxe2x80x9d containers, which can be partially unscrewed to move the top of the cap away from the top of the head and thus release a central orifice through which the product can be distributed.
Thus, U.S. Pat. No. 5,199,605 registered by the applicant describes a distributor for cream or paste products comprising a rigid head fixed onto a body or a skirt and an overcap. The following description uses the same references used in the figures in U.S. Pat. No. 5,199,605. The head (1) and the overcap (2) comprise complementary screwing means (9 and 19) that rotate relative to each other to raise or lower the overcap with respect to the head. The overcap is provided with a central opening (14) and the top end of the head is in the form of a cylindrical neck (5) through which the product passes, closed by a closer (3) supported by tabs (4) fixed to the inside wall of the neck. The closer closes the central opening of the overcap when this overcap is in the down position.
Rotation is limited firstly by the end of the thread at the end of screwing in, and secondly by pads (24) located on the shoulder (11) of the distributor when screwing out and that work in cooperation with the ends (26 and 25) of axial reinforcing ribs (260 and 250) of the skirt (16) of the overcap. The shapes of the ends (25) and (26) are different. The end (25) is small but rigid, and stops in contact with a pad (24) that participates in blocking at the end of screwing in and protects the end of the thread. The end (26) is a circumferentially flexible plate that is fixed from above (240) by a pad (24) and is then suddenly released, and which vibrates and acts as a warning at the end of screwing out. The blocking means used are only efficient if the forces applied are small, particularly due to their size and the low stiffness of the assembly. Due to the warning, the user reduces and then stops applying a force when the overcap is close to a stop.
It is difficult to manufacture the distributor described above, particularly due to moulding of the central part of the head, namely the closer held in place at the end of the tabs fixed onto the internal wall of the neck. The tooling is complex, particularly to make the arms that hold the closer in place, which have to be as thin as possible so that the product can pass through easilyxe2x80x94and consequently cannot be used as feed ducts for the plastic material leading from a central injection point. In this case, peripheral injection is necessary at several points around the wall of the neck, and the wall cannot be as thin as would have been desirable.
Furthermore, safety when screwing out remains uncertain despite the audible warning. The applicant considered replacing the xe2x80x9cpadxe2x80x94end of groovesxe2x80x9d device by a device such as that proposed in EP 0 633 197 in which, during screwing out, a flexible axial plate (12) fixed to the overcap reaches a stop in contact with a profiled axial portion (14) attached to the shoulder of the distributor. Another profiled axial portion (15) acts as a stop with a plate (12) that is flexible in the screwing in direction. In the case of EP 0 633 197, the objective is to make axial portions (14) and (15) as close to each other as possible to fix the overcap firmly in place. Moving the profiled axial portions (15) and (14) away from each other enables a limited relative rotation of the overcap and the head. But these profiled axial portions are thick and high which further increases the weight of plastic material to be injected on the head, which has a particularly negative effect on production rates, particularly when the head is directly insert moulded on the skirt or the body of the container, in other words when the head is fixed to the body or the skirt at the same time that it is injected.
Finally, the thick and heavy head makes the tube cumbersome to handle, which is not appreciated by the user of the container. The size of a device that cannot be unscrewed accidentally and with limited rotation such as any of the devices according to prior art is such that it is impossible to equip the head with other means that could perform other functions.
For example, it would be necessary to improve the stop at the end of screwing in since the flexibility of the plastic materials used for the neck and the overcap means that if the end of screwing in force is not controlled, the helical thickening forming the thread can easily skip from one helical groove to the next, with sudden movements of the overcap with respect to the head.
The seal provided by a system such as the xe2x80x9ccenterlockxe2x80x9d is not excellent. For applications such as cosmetic or pharmaceutical products packaged in flexible tubes, it is usually necessary to use an outer cover to prevent unwanted leaks, particularly when these tubes are transported in a carry bag. Apart from the additional cost, the use of an outer cover further slightly increases the weight of the container at its distribution head. No solution based on the xe2x80x9ccenterlockxe2x80x9d principle has been considered up to now for products sensitive to ambient air such as cyanoacrylate glues, due to the excessive risk of glue setting in the distribution orifice.
Therefore, the applicant attempted to develop a lightweight head+overcap assembly that is compact and easy-to-inject, in which the overcap is irreversibly fixed to the head in the axial direction and to which a limited rotation can be imposed, in other words by blocking the overcap in clearly defined positions when screwing in and screwing out. The weight reduction and the compactness of this fixing system not only makes containers according to prior art easier to use, they also make it possible to create new containers for more demanding applications, particularly for impermeability of the closure, by the addition of elements that perform other functions.
FIG. 1 diagrammatically shows the various attachment means to facilitate understanding of the description of the invention. It shows a top view of a head above a cylindrical wall (50) provided with attachment means (11, 12, 15) cooperating with the attachment means (33 and 34) on the overcap, the other parts of the said overcap not being shown.
The purpose of the invention is a container head and overcap assembly, the said head having one end open and designed to be fixed on the open ends of a container or flexible tube fitted with a cylindrical neck (20) and a shoulder (3) extending from the said open end to the base (10) of the neck, in which the cylindrical neck is provided with at least one helical screw thread (21) with pitch P and in which the overcap has a cylindrical skirt (35) provided with a screwing in means (36) on its inner wall complementary to the screwing in means on the neck. The overcap has a top wall (46) on which at least one radially flexible and circumferentially rigid axial plate (33) is fixed. The other end of this flexible plate is free. The plate is located at a distance from the centreline of the overcap that is slightly greater than the outside radius of the neck. The bottom of the neck is provided with at least one opening stop (12) with angular position xcex8, and at least one closure stop (11) with angular position xcfx86 that is not as high, the said opening stop being provided with a first wall (14) that gradually moves away from the cylindrical wall of the said neck, such that when the overcap is screwed onto the head for putting the assembly together, the free end of the axial plate (33) comes into contact with the first wall (14) of the opening stop (12) and in that the axial plate (33), the free end of which is moved centrifugally, is elastically deformed. After passing beyond the angular position xcex8, the flexible plate (33) moves beyond towards the wall of the neck in a space between the said opening and closure stops, and in this case its movement is limited by the blocking walls (16 and 17) of the stops (11 and 12).
The axial plate (33) is radially flexible in the sense that its free end moves elastically under the effect of a small force in the radial direction and is circumferentially rigid in the sense that a very large force has to be applied to move this free end in the orthoradial direction, and this force is sufficiently high to cause irreversible deformation or breakage of the said plate.
Preferably, the axial plate (33) matches the shape of a portion of the ring with an opening angle 5 and average radius slightly greater than the radius of the neck. Its orthogonal section is a curved trapezium in which the small base and the large base are arcs of a circle, the large base being on the inside. The small base and the large base are associated with the cylindrical walls of the plate, the other sides are associated with the cross-thickness walls (47 and 48) of the said plate.
In order to facilitate fixing by stops, the blocking walls of the stops do not bear on diametric axial planes, but are slightly inclined with respect to these planes. Thus, for the closure stop (11) at angular position xcfx86, the blocking wall (16) of the stop makes an angle (xcfx80/2xe2x88x92xcex31) with the diametric axial plane with angular position xcfx86, and for the opening stop (12) at angular position xcex8, the blocking wall (17) of the stop forms an angle (xcfx80/2xe2x88x92xcex32) with the diametric axial plane at angular position xcex8. For the plate, its cross-thickness walls (47 and 48) are not orthogonal with the cylindrical walls but each forms an angle (xcex51 and xcex52) with the diametric axial plane passing through the lower end at the corresponding angle (xcfx80/2xe2x88x92xcex31) or (xcfx80/2xe2x88x92xcex32), such that fixing is achieved when one of these cross-thickness walls is inserted in the dihedron comprising of the wall of the neck and the blocking wall of the corresponding stop.
Preferably, the height difference between the said opening and closure stops is equal to at least P*(|xcex8xe2x88x92xcfx86|xe2x88x92xcex4)/2xcfx80.
The opening stop is fairly high and is preferably a ratchet tooth with an acute angle xcex32. The closure stop may also be a ratchet tooth oriented in the opposite direction with an acute angle xcex31, but an anchor stop with an L-shaped section is preferred if possible according to the dimensions; the blocking wall of the stop is used with a circumferential wall that traps the end of the axial plate, this end being inherently flexible in the radial direction to pass above the opening stop when screwing in the assembly and that could skip above the closure stop in the absence of this circumferential wall. Furthermore, the circumferential wall increases the friction area offered in contact with the axial plate, which improves the braking effect that occurs when close to the stop, improves retention of the axial plate in contact with the said stop and therefore improves retention of the overcap in the closed position.
The head and the overcap are preferably made of a thermoplastic material. The axial plate is advantageously moulded along the extension of the cylindrical skirt of the overcap. This skirt is provided with a screwing in means (for example one or several xe2x80x9cnutxe2x80x9d type threads) on its internal wall complementary to the screwing in means on the neck that comprises one or several helical threads (xe2x80x9cscrewxe2x80x9d type threads). The skirt of the overcap must be rigid enough so that the xe2x80x9cnutxe2x80x9d type threads do not skip above the xe2x80x9cscrewxe2x80x9d type threads. Consequently, the skirt of the overcap is advantageously reinforced by axial radial ribs if possible, depending on the size.
It is advantageous to mould a helical xe2x80x9cscrewxe2x80x9d thread with a straight starting point on the neck, and a xe2x80x9cnutxe2x80x9d thread with a straight stopping point on the internal wall of the overcap skirt, to cooperate with the closure stop and to lock rotation of the overcap.
If the axial plate is moulded along the continuation of the line of the skirt, and if possible depending on the dimensions, the radial ribs that reinforce the skirt may also be prolonged, fixed to the outside wall of the axial plate to act as an audible warning as in U.S. Pat. No. 5,199,605, rather than to make the wall less flexible; a slit separates the end of the radial axial rib from the end of the axial plate. A pad is placed on the shoulder at the same distance from the axis as the said end of the rib and at an angle xcex1 of more than 10xc2x0, for example about 20xc2x0, from the opening stop (in the screwing in direction) or the closure stop (in the screwing out direction) in order to make the end of this axial rib vibrate. The audible warning may be provided for closing and opening. However in practice, it is not desirable to have too many audible effects for a limited rotation angle since it is no longer possible to identify the warning if they are too close. Thus, it is preferable to use a warning device only at one stop.
For the other stop on which there is no audible warning, a braking effect could be provided close to the stop; the user would feels a slight resistance to inform him or her that the overcap will shortly arrive at its stop. This braking effect is achieved by forming a wall that moves away from the cylindrical wall of the neck close to the stop in the limited rotation range. FIG. 1 illustrates a helical separation with angle xcex2 between the axial plane tangent to the said wall and the axial plane tangent to the neck. This angle is necessarily small, to the extent that the radial height of the stop must be sufficient to maintain its blocking efficiency.
Each part of the head+overcap assembly according to the invention is made separately, preferably by the injection of a thermoplastic material in a mould. The head may be fixed to the open end of a container or a tube skirt at the time that it is formed (insert moulding). The assembly is then installed by screwing the overcap on the head.
Due to the dimensional manufacturing tolerances, the screwing in angle that brings the axial plate into a limited rotation range during assembly (in other words the space between the opening and closure stops) is not perfectly repetitive, which is a handicap for large production series. n sets of stops could be made on the head in order to maintain maximum flexibility in manufacturing at high production rates, with the closure stop being located along the radial extension of the opening stop, but not as high. The limited rotation is then (2Π/n)xe2x88x92xcex4 if there are n (opening stop, closure stop) pairs on the shoulder and n axial plates on the overcap. Thus, if the axial plate that is radially flexible overlapped a stop, it will be located in a new trapping area offset from the previous trapping area by (2Π/n).
Furthermore, cooperation of n plate blocking points enables the use of lower radial stops and more compact plates. But if the stops are to remain efficient, the range of their blocking wall, an approximately diametric portion of an axial plane, must be sufficiently large, which imposes a minimum radial height, taking account of the necessary clearance between the inner cylindrical wall of the plate and the outer cylindrical wall of the neck, and taking account of the inevitable fillets equal of a few tenths of a millimeter on the moulded convex parts of stops and the plate. In practice, the objective is that the radial height of the stop should be such that the firm fixed stop area is equal to the clearance between the inner cylindrical wall of the plate and the outer cylindrical wall of the neck.
The head of the container or the tube may or may not be made of plastic, for various reasons. In this case, the assembly according to the invention is in the form of a xe2x80x9cbase+overcapxe2x80x9d assembly, the base being an intermediate part with elements characteristic of the head described in this invention in its upper part, and non-plastic attachment means to the head in its lower part.
In the following examples, we have chosen flexible tubes with small dimensions such that the preferred number n of pairs of opening/closure stops is equal to 2.
In examples 1 and 2, it can be seen that the small size and low weight possible due to these opening/closure stops and these flexible plates makes xe2x80x9ccenterlockxe2x80x9d systems more comfortable in use.
In examples 3 and 4, elements are added to perform additional functions, and introducing new flexible tubes; the first is a sun cream distributor in which sun cream is distributed by the deformation of an elastomeric wall, and has a head which makes the closure perfectly safe when the tube is placed in a carry bag even without an outer cap, and the second is a metallic distribution tube for a cyanoacrylate based glue that is very sensitive to humidity.